/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.transforms;



import com.bff.gaia.unified.sdk.annotations.Experimental;

import com.bff.gaia.unified.sdk.annotations.Experimental.Kind;

import com.bff.gaia.unified.sdk.values.PCollectionView;

import com.bff.gaia.unified.vendor.guava.com.google.common.collect.Sets;



import java.io.Serializable;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.Set;



/** Describes the run-time requirements of a {@link Contextful}, such as access to side inputs. */

@Experimental(Kind.CONTEXTFUL)

public final class Requirements implements Serializable {

  private final Collection<PCollectionView<?>> sideInputs;



  private Requirements(Collection<PCollectionView<?>> sideInputs) {

    this.sideInputs = sideInputs;

  }



  /** The side inputs that this {@link Contextful} needs access to. */

  public Collection<PCollectionView<?>> getSideInputs() {

    return sideInputs;

  }



  /** Describes the need for access to the given side inputs. */

  public static Requirements requiresSideInputs(Collection<PCollectionView<?>> sideInputs) {

    return new Requirements(sideInputs);

  }



  /** Like {@link #requiresSideInputs(Collection)}. */

  public static Requirements requiresSideInputs(PCollectionView<?>... sideInputs) {

    return requiresSideInputs(Arrays.asList(sideInputs));

  }



  /** Describes an empty set of requirements. */

  public static Requirements empty() {

    return new Requirements(Collections.emptyList());

  }



  /** Whether this is an empty set of requirements. */

  public boolean isEmpty() {

    return sideInputs.isEmpty();

  }



  public static Requirements union(Contextful... contextfuls) {

    Set<PCollectionView<?>> sideInputs = Sets.newHashSet();

    for (Contextful c : contextfuls) {

      sideInputs.addAll(c.getRequirements().getSideInputs());

    }

    return requiresSideInputs(sideInputs);

  }

}